Obviously there' infinite kamae but for high energy applications a 60 or 90 deg angle doesn't provide enough support. For yokomennage and shomennage a modified zenkutsu dachi works really well. When these strikes/throws are trained with other forms in sets, kata, or freestyle then ‘shallower' stances are ideal to facilitate transitions between forms. A right or left hanmi from 45 deg up to 0 deg (feet parallel) and all the way through to sanchin dachi can be used. O Sensei's height gave him the advantage of being able to ground with short distances between his feet, yet his historical video does show times where he opts to accommodate ground with his upper body instead of his kamae. O Sensei must have practiced it considerably, shown in the contraction and protrusion of his shoulders at strike termination, that it's been passed down and canonized in the Iwama line. It's important to note though the majority of his kata/freestyle rarely included shoulder resistance. The time commitment to release back into full non-resistance from resistance is a limiting factor, not to mention Aikido's understanding of non-resistance being the base of all action.